Results 1 to 6 of 6

Math Help - Trig identities

  1. #1
    Junior Member
    Joined
    Sep 2006
    Posts
    38

    Trig identities

    can anyone help with this problem?
    Prove

    tan^2 + cos^2 + sin^2 = 1/cos^2
    Last edited by imthatgirl; January 10th 2007 at 06:09 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Global Moderator

    Joined
    Nov 2005
    From
    New York City
    Posts
    10,616
    Thanks
    9
    Quote Originally Posted by imthatgirl View Post
    can anyone help with any of these problems?
    Prove
    a) (tan^2) /( 1+tan^2) = sin^2
    1+\tan^2 x=\sec ^2 x
    Thus,
    \frac{\tan ^2 x}{\sec^2 x}
    \frac{(\sin^2 x/\cos^2 x)}{(1/\cos^2 x)}
    Simplify fraction,
    \sin^2 x
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Global Moderator

    Joined
    Nov 2005
    From
    New York City
    Posts
    10,616
    Thanks
    9
    Quote Originally Posted by imthatgirl View Post

    b) tan^2 - cos^2 = 1/(cos^2) - 1 - cos^2
    \tan^2 x - \cos^2 x= \frac{1}{\cos ^2 x}- 1 -\cos ^2 x

    (\sec^2 x-1)-\cos^2 x=\frac{1}{\cos^2 x}-1-\cos^2 x

    \sec^2 x - 1 - \cos^2 x= \frac{1}{\cos^2 x}-1 -\cos^2 x

    \frac{1}{\cos^2 x}-1-\cos^2 x = \frac{1}{\cos^2 x}-1 -\cos^2 x
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Sep 2006
    Posts
    38
    thank you so much for the help i get it now
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,829
    Thanks
    123
    Quote Originally Posted by imthatgirl View Post
    can anyone help with this problem?
    Prove

    tan^2 + cos^2 + sin^2 = 1/cos^2
    Hello,

    you have to use these properties:

    \cos^2(x)+\sin^2(x)=1
    \tan(x)=\frac{\sin(x)}{\cos(x)}

    \tan^2(x)+\cos^2(x)+\sin^2(x)=\tan^2(x)+1-\sin^2(x)+\sin^2(x)= <br />
\tan^2(x)+1=\frac{\sin^2(x)}{\cos^2(x)}+1=\frac{\s  in^2(x)+\cos^2(x)}{\cos^2(x)}=\frac{1}{\cos^2(x)}

    EB

    PS: If you have a new problem please start a new thread. Otherwise you risk that nobody will notice that you asked for some help.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,902
    Thanks
    329
    Awards
    1
    I'll reinforce that comment. If you remove your original question then no one can see what you originally posted and thus be confused about what someone's response to it is. If someone else is looking for help on a similar topic, that makes it harder for them to learn it themselves. So please, when you have a new question either post a completely new thread, or just respond to the post you already started.

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trig Identities
    Posted in the Calculus Forum
    Replies: 2
    Last Post: December 3rd 2009, 06:44 AM
  2. Trig identities
    Posted in the Trigonometry Forum
    Replies: 6
    Last Post: June 22nd 2009, 06:58 AM
  3. Trig Identities
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: November 9th 2008, 04:35 PM
  4. Trig Identities
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: November 7th 2008, 08:25 PM
  5. Trig Identities Help!!!!
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: April 14th 2008, 11:47 AM

Search Tags


/mathhelpforum @mathhelpforum